1. Field of the Invention
Embodiments of the invention relate to apparatuses that combine sensor and infusion elements and to methods for using such apparatuses within the body of a patient.
2. Description of Related Art
Insulin must be provided to people with Type 1 and many with Type 2 diabetes. Traditionally, since it cannot be taken orally, insulin has been injected with a syringe. More recently, use of external infusion pump therapy has been increasing, especially for delivering insulin for diabetics using devices worn on a belt, in a pocket, or the like, with the insulin delivered via a catheter with a percutaneous needle or cannula placed in the subcutaneous tissue. For example, as of 1995, less than 5% of Type 1 diabetics in the United States were using pump therapy. There are now about 12% of the currently over 1,000,000 Type 1 diabetics in the U.S. using insulin pump therapy, and the percentage is now growing at an absolute rate of over 2% each year. Moreover, the number of Type 1 diabetics is growing at 3% or more per year. In addition, growing numbers of insulin using Type 2 diabetics are also using external insulin infusion pumps. Physicians have recognized that continuous infusion provides greater control of a diabetic's condition, and are also increasingly prescribing it for patients. In addition, medication pump therapy is becoming more important for the treatment and control of other medical conditions, such as pulmonary hypertension, HIV and cancer.
Pump therapy systems have been developed that deliver medication by infusion into subcutaneous tissue using an infusion set with needles and/or a soft cannula. The soft cannula of the infusion set is normally inserted into the skin with a needle to prevent kinking of the soft cannula. Automatic insertion devices have been utilized to reduce the discomfort and pain involved with the insertion of infusion sets.
In addition to delivering medication to a patient, a number of other medical devices have been designed to determine body characteristics by obtaining a sample of bodily fluid. A variety of implantable electrochemical sensors have been developed for detecting and/or quantifying specific agents or compositions in a patient's blood. For instance, glucose sensors have been developed for use in obtaining an indication of blood glucose levels in a diabetic patient. Such readings can be especially useful in monitoring and/or adjusting a treatment regimen that typically includes the regular administration of insulin to the patient. Thus, blood glucose readings are particularly useful in improving medical therapies with semi-automated medication infusion pumps of the external type, as generally described in U.S. Pat. Nos. 4,562,751; 4,678,408; and 4,685,903; or automated implantable medication infusion pumps, as generally described in U.S. Pat. No. 4,573,994, all of which are specifically incorporated by reference herein.